Semiconductor elements in semiconductor-element packages are getting thinner and larger in recent years. When the semiconductor elements are fixed on resin package substrates, a difference between a thermal expansion coefficient of the semiconductor elements and that of the package substrates causes inconvenience: the semiconductor elements hardly deflect because of heat, whereas the package substrates deflect or bend because of heat. This inconvenience may cause disconnection in electrical joint portions of the semiconductor elements and the package substrates.
Stainless or copper stiffening members (hereinafter, referred to as stiffeners) are attached on the package substrates to reduce the thermal deflection or bending of the package substrates. In this way, disconnection is avoided in the electrical joint portions of the semiconductor elements and the package substrates.
However, the foregoing related art has following disadvantages. More specifically, in the semiconductor-element packages, capacitors are generally arranged on a surface of the package substrates opposite to a surface mounting the semiconductor elements to face the semiconductor elements for better electric performance. To avoid interference between the capacitors and circuit boards for mounting the semiconductor-element packages, low-profile capacitors are used. Additionally, a hole is bored or countersunk at a portion of the circuit boards that interferes with the capacitors.
Since the low-profile capacitors are expensive, the use of the low-profile capacitors unfortunately increases a fabrication cost of the semiconductor-element packages. Additionally, boring or countersinking a hole in the circuit boards unfortunately decreases electric performance of the semiconductor-element packages and the circuit boards.
The decrease in the electric performance indicates the following. For example, when a wire for supplying electric power to the semiconductor-element packages is arranged to detour around the bored or countersunk portion, the wire becomes longer than other wires for supplying electric power. Since voltage drops in proportion to length of a wire, it becomes difficult to maintain potentials of the wires having different lengths at a uniform level.
The followings are reference documents.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2000-323610    [Patent Document 2] Japanese Laid-open Patent Publication No. 2004-289133